Elastic wave device and electronic component

Abstract

To provide an elastic wave device that is small sized and in which a frequency fluctuation due to a change with time hardly occurs, and an electronic component using the above elastic wave device. A trapping energy mode portion 2 provided in an elastic wave waveguide 10 made of a piezoelectric material excites a second elastic wave being an elastic wave in a trapping energy mode by a specific frequency component included in a first elastic wave being an elastic wave such as a SAW propagated from a first propagation mode portion 4 , and a cutoff portion 3 provided in a peripheral region of the trapping energy mode portion 2 has a cutoff frequency being a frequency higher than that of the second elastic wave. A second propagation mode portion mode-converts the second elastic wave leaked through the cutoff portion to a third elastic wave being the elastic wave in the propagation mode to propagate the third elastic wave.

1. An elastic wave device comprising:
 a first propagation mode portion provided in an elastic wave waveguide and provided with a first IDT electrode for making a piezoelectric material excite a first elastic wave being an elastic wave in a propagation mode; 
 a trapping energy mode portion provided in the elastic wave waveguide and in which a second elastic wave being an elastic wave in a trapping energy mode is excited by a specific frequency component included in the first elastic wave propagated from the first propagation mode portion; 
 a cutoff portion provided in a peripheral region of the trapping energy mode portion and having a cutoff frequency being a frequency higher than that of the second elastic wave; and 
 a second propagation mode portion provided at a position adjacent to the trapping energy mode portion across the cutoff portion along a direction in which the first elastic wave propagates, and mode-converting the second elastic wave leaked through the cutoff portion to a third elastic wave being the elastic wave in the propagation mode to propagate the third elastic wave, and provided with a second IDT electrode for taking the third elastic wave out of the piezoelectric material as an electrical signal. 
 
     
     
       2. The elastic wave device according to  claim 1 , wherein
 the first propagation mode portion is also used as the second propagation mode portion. 
 
     
     
       3. The elastic wave device according to  claim 1 , wherein
 an elastic wave waveguide for reference provided with a third IDT electrode for making the piezoelectric material excite an elastic wave for reference and a fourth IDT electrode provided in a propagation direction of the elastic wave for reference in order to take an electrical signal in opposite phase to an electrical signal taken out in the second IDT electrode after the first elastic wave passes through the first propagation mode portion and the second propagation mode portion out of the elastic wave for reference via the piezoelectric material, is provided parallel to the elastic wave waveguide via an isolation zone of an elastic wave, and a differential signal made after the electrical signal taken out of the second IDT electrode and the electrical signal taken out of the fourth IDT electrode are added is obtained. 
 
     
     
       4. An elastic wave device comprising:
 a first propagation mode portion provided in a first elastic wave waveguide and provided with a first IDT electrode for making a piezoelectric material excite a first elastic wave being an elastic wave in a propagation mode; 
 a trapping energy mode portion provided in the first elastic wave waveguide and in which a second elastic wave being an elastic wave in a trapping energy mode is excited by a specific frequency component included in the first elastic wave propagated from the first propagation mode portion; 
 a cutoff portion provided in a peripheral region of the trapping energy mode portion and having a cutoff frequency being a frequency higher than that of the second elastic wave; 
 a second elastic wave waveguide adjacent to the first elastic wave waveguide in a direction perpendicular to a traveling direction of the first elastic wave; 
 a second IDT electrode provided in the second elastic wave waveguide; and 
 an isolation zone of an elastic wave provided between the first elastic wave waveguide and the second elastic wave waveguide and provided with a cutout portion having one portion thereof cut out, and wherein 
 a third elastic wave being the elastic wave in the propagation mode obtained by reflecting the first elastic wave in the cutoff portion and the trapping energy mode portion is passed through the isolation zone via the cutout portion, and then the third elastic wave is received in the second IDT electrode to be taken out of the piezoelectric material as an electrical signal, and a region where the third elastic wave propagates is set as a second propagation mode portion. 
 
     
     
       5. The elastic wave device according to  claim 1 , wherein
 the first IDT electrode and the second IDT electrode are provided on a front surface of the piezoelectric material and the first elastic wave and the third elastic wave are surface acoustic waves. 
 
     
     
       6. The elastic wave device according to  claim 1 , wherein
 the cutoff portion is formed to have a cutoff frequency being a frequency higher than that of the second elastic wave because a thickness of the elastic wave waveguide constituting the cutoff portion is thinner than that of the elastic wave waveguide constituting the trapping energy mode portion. 
 
     
     
       7. The elastic wave device according to  claim 1 , wherein
 the elastic wave waveguide is formed in a manner that a thickness of an outer region of the cutoff portion is thicker than that of the cutoff portion. 
 
     
     
       8. The elastic wave device according to  claim 1 , wherein
 the elastic wave waveguide is made of a piezoelectric material. 
 
     
     
       9. The elastic wave device according to  claim 1 , wherein
 the piezoelectric material is a piezoelectric film provided on an upper surface side of an IDT electrode formed on an elastic wave waveguide made of a non-piezoelectric material, or is a piezoelectric film provided between an elastic wave waveguide made of a non-piezoelectric material and an IDT electrode. 
 
     
     
       10. The elastic wave device according to  claim 1 , wherein
 the trapping energy mode portion is formed in a flat plate shape. 
 
     
     
       11. The elastic wave device according to  claim 1 , wherein
 the trapping energy mode portion is formed in a plano-convex lens shape. 
 
     
     
       12. The elastic wave device according to  claim 1 , wherein
 the trapping energy mode portion is formed in a manner that a planar shape thereof is a polygon with four or more angles, or a circle, or an ellipse. 
 
     
     
       13. The elastic wave device according to  claim 1 , wherein
 at least one of the first IDT electrode and the second IDT electrode is made of a uni-directional transducer electrode. 
 
     
     
       14. The elastic wave device according to  claim 1 , further comprising:
 two or more trapping energy mode portions whose peripheries are each surrounded by the cutoff portion, and wherein 
 the trapping energy mode portions are provided adjacently to each other or one another in the propagation direction of the elastic wave in the propagation mode or in a direction perpendicular to the propagation direction to enable second elastic waves to be excited in the respective trapping energy mode portions to be coupled to each other or one another, and thereby a multi-mode coupled filter is constituted. 
 
     
     
       15. An electronic component comprising:
 the elastic wave device according to  claims 1 . 
 
     
     
       16. The elastic wave device according to  claim 4 , wherein
 the first IDT electrode and the second IDT electrode are provided on a front surface of the piezoelectric material and the first elastic wave and the third elastic wave are surface acoustic waves. 
 
     
     
       17. The elastic wave device according to  claim 4 , wherein
 the cutoff portion is formed to have a cutoff frequency being a frequency higher than that of the second elastic wave because a thickness of the elastic wave waveguide constituting the cutoff portion is thinner than that of the elastic wave waveguide constituting the trapping energy mode portion. 
 
     
     
       18. The elastic wave device according to  claim 4 , wherein
 the elastic wave waveguide is formed in a manner that a thickness of an outer region of the cutoff portion is thicker than that of the cutoff portion. 
 
     
     
       19. The elastic wave device according to  claim 4 , wherein
 the elastic wave waveguide is made of a piezoelectric material. 
 
     
     
       20. The elastic wave device according to  claim 4 , wherein
 the piezoelectric material is a piezoelectric film provided on an upper surface side of an IDT electrode formed on an elastic wave waveguide made of a non-piezoelectric material, or is a piezoelectric film provided between an elastic wave waveguide made of a non-piezoelectric material and an IDT electrode. 
 
     
     
       21. The elastic wave device according to  claim 4 , wherein
 the trapping energy mode portion is formed in a flat plate shape. 
 
     
     
       22. The elastic wave device according to  claim 4 , wherein
 the trapping energy mode portion is formed in a plano-convex lens shape. 
 
     
     
       23. The elastic wave device according to  claim 4 , wherein
 the trapping energy mode portion is formed in a manner that a planar shape thereof is a polygon with four or more angles, or a circle, or an ellipse. 
 
     
     
       24. The elastic wave device according to  claim 4 , wherein
 at least one of the first IDT electrode and the second IDT electrode is made of a uni-directional transducer electrode. 
 
     
     
       25. The elastic wave device according to  claim 4 , further comprising:
 two or more trapping energy mode portions whose peripheries are each surrounded by the cutoff portion, and wherein 
 the trapping energy mode portions are provided adjacently to each other or one another in the propagation direction of the elastic wave in the propagation mode or in a direction perpendicular to the propagation direction to enable second elastic waves to be excited in the respective trapping energy mode portions to be coupled to each other or one another, and thereby a multi-mode coupled filter is constituted. 
 
     
     
       26. An electronic component comprising:
 the elastic wave device according to  claims 4 . 
 
     
     
       27. The elastic wave device according to  claim 1 , wherein
 the second elastic wave is an elastic wave in a high-order trapping energy mode. 
 
     
     
       28. The elastic wave device according to  claim 4 , wherein
 the second elastic wave is an elastic wave in a high-order trapping energy mode. 
 
     
     
       29. The elastic wave device according to  claim 1 , wherein
 an adsorption layer to adsorb a substance to be sensed is formed on a front surface of the trapping energy mode portion. 
 
     
     
       30. The elastic wave device according to  claim 4 , wherein
 an adsorption layer to adsorb a substance to be sensed is formed on a front surface of the trapping energy mode portion.